In many diseases, cell death is mediated through apoptotic and/or necrotic pathways. While much is known about the mechanisms of action that control apoptosis, control of necrosis is not as well understood. Understanding the mechanisms regulating both necrosis and apoptosis in cells is essential to being able to treat conditions, such as neurodegenerative diseases, stroke, coronary heart disease, kidney disease, and liver disease. A thorough understanding of necrotic and apoptotic cell death pathways is also crucial to treating AIDS and the conditions associated with AIDS, such as retinal necrosis.
Cell death has traditionally been categorized as either apoptotic or necrotic based on morphological characteristics (Wylie et al., Int. Rev. Cytol. 68: 251 (1980)). These two modes of cell death were also initially thought to occur via regulated (caspase-dependent) and non-regulated processes, respectively. More recent studies, however, demonstrate that the underlying cell death mechanisms resulting in these two phenotypes are much more complicated and, under some circumstances, interrelated. Furthermore, conditions that lead to necrosis can occur by either regulated caspase-independent or non-regulated processes.
One regulated caspase-independent cell death pathway with morphological features resembling necrosis, called necroptosis, has recently been described (Degterev et al., Nat. Chem. Biol. 1:112 (2005)). This manner of cell death can be initiated with various stimuli (e.g., TNF-α and Fas ligand) and in an array of cell types (e.g., monocytes, fibroblasts, lymphocytes, macrophages, epithelial cells and neurons). Necroptosis may represent a significant contributor to and, in some cases, predominant mode of cellular demise under pathological conditions involving excessive cell stress, rapid energy loss, and massive oxidative species generation, where the highly energy-dependent apoptosis process is not operative.
The identification and optimization of low molecular weight molecules capable of inhibiting necroptosis will assist in elucidating its role in disease patho-physiology and could provide compounds (i.e., necrostatins) for anti-necroptosis therapeutics. The discovery of compounds that prevent caspase-independent cell death (e.g., necrosis or necroptosis) would also provide useful therapeutic agents for treating or preventing conditions in which necrosis occurs. These compounds and methods would be particularly useful for the treatment of neurodegenerative diseases, ischemic brain and heart injuries, and head trauma.